This invention relates to a nibbling tool for shearing sheet material and more particularly to a hand held tool which may have its own complete drive or have a drive means comprising a rotary drive shaft designed to be coupled to an external drive means, for example the chuck of a conventional electric drill.
Nibbling tools for shearing a channel in sheet material by relative movement between the tool and material in a direction along the channel are known, for example from U.K. Specification Nos. 636983, 1485795 and 2099744, comprising a body, a punch, drive means for reciprocating the punch and a die defining a channel for guiding the punch for reciprocating movement, the punch and die having co-operating curved cutting edges extending transversely to the channel to be cut such that each reciprocating movement of the punch removes a crescent shaped chip of material so as to extend the channel. Normally a drive shaft is mounted in the body for rotation about its axis and coupling means couple the punch and drive shaft to convert the rotational movement to linear reciprocation of the punch.
Preferably the die has a lower guide portion in which the lower end of the punch is guided and this is connected to the main body portion of the die by a narrow web portion.